Compression and water/coolant in cylinder

Long story short I was replacing spark plugs and found coolant in cylinder #1 from when I winterized it. Mercruiser 454 (L621109) raw water cooled. Compression in that cylinder after cleaning it out is excessive I believe. Between 200 and 225psi. The next cylinder #3 is only Between 50 and 75psi. Very low. All the others are ok I believe, they are in the 120-160 range. I'm thinking a new head and all gaskets but I'm just wondering if I'm missing anything. Used in salt water if that matters and roughly 1'000 hours on the motor. Any help would be greatly appreciated.

Do you have the manual? Water in engine troubleshooting guide is on page 1C-22. If you need a pdf copy of the manual you can get one here:
https://marine.needmanual.com/1993-...-marine-engines-service-manual-number-16.html

It would seem that a head gasket is in your future but it's too early to say for sure.

Head rebuild or replace and gasket should do it... however... many feel that 1000 hrs on a sea water cooled engine is about it. Have seen engines where a couple of square inches of block wall under the heads just rusts out and falls out without any warning. Just sayin'.... I'd tap the block walls (and ends) with the ball end of a ball peen hammer to check it out before investing bucks in a rebuild.
Pay special attention to the "freeze out" plugs as well.